This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-313547 filed on Oct. 13, 2000.
The present invention relates to a semiconductor device that includes a concave made on a side of the semiconductor device and a plurality of thin-film sensing areas in a thin film area formed on the back side of a bottom of the concave and to a fabrication method of the device.
One of the related semiconductor devices is a thermopile infrared sensor that makes it possible to measure quickly a temperature of an object without contacting. This type of infrared sensor has a plurality of sensing areas in a thin film area to measure temperatures at a plurality of places on an object. In that case, a thin film area needed is so wide that the thin film area becomes weak enough to cause a damage of the thin film during a sensor fabrication or in use. Thickening to reinforce the thin film area is undesirable because the thin film area should suppress thermal conduction of the sensing areas.
An infrared sensor with a rim made from a Boron-doped-etch-stop layer under an alley between the sensing areas is proposed to support the thin film area. The layer however requires high concentration doping of an impurity, such as 1019 cmxe2x88x923 to 1020 cmxe2x88x923 or more. As a result, the thin-film sensing areas tend to deform due to a stress in the rim caused by the high concentration doping and the rim tends to be weakened because crystal defects in the rim are increased by the high concentration doping.
It is an object of this invention to reduce deformation of thin-film sensing areas caused by a stress in a rim made for supporting the thin-film sensing areas that are formed on a silicon substrate of a semiconductor device and to reinforce the rim.
According to the present invention, an anisotropic etching is applied to a semiconductor substrate to form a rim for supporting a thin film area. The rim is formed by leaving an unetched portion of the substrate by means of masking a section on the back side of an alley between the sensing areas or by creating an electrochemically etch-proof region under an alley between the sensing areas. As a result, high concentration Boron doping such as 1019 cmxe2x88x923 to 1020 cmxe2x88x923 or more is not required. Thus, it is possible to reduce deformation of thin-film sensing areas caused by a stress in a rim and to reinforce the rim.